- This exchange:
Donnie: How does it feel to have a wacko for a son?
Rose: It feels wonderful.
- Donnie's perpetual basket-case look can be this, especially if you are mentally ill yourself and know what it feels like to be constantly strung out.
- The ending is this completely. The worst part is when they show Frank at the end of the "Mad World" montage just sitting there. Implying that, seeing as the other people in said montage remembered Donnie in some way, he's going to skip Halloween to remember someone he never even knew. To top it off, he tried to warn that person and failed. Now imagine how you would feel in his shoes.
- Donnie lets himself get crushed to death by the airplane, because if he doesn't, the world will end on Halloween night Then, the song "Mad World" starts playing at the credits, and you really start to lose it.
- The shot scanning Donnie's family at the end. They all look simultaneously gutted and disconnected, unable to comprehend what's happening. Made worse by contrasting it with the beginning. The authorities couldn't find the airplane the fuselage came from because it's from an alternate universe, and we have no indication they remember that Donnie chose this. Not only is a member of their family dead, horribly and before he's even out of high school, but they will never know why.
- The part that really got to me (it may have only been in the director's cut) was when Donnie gets into a debate in his English class over Watership Down, asking why the reader should care if the stupid rabbits live or die, and he sounds pretty desperate. He is so clearly trying not to be the Messiah, to convince himself he shouldn't have to die for these foolish, ungrateful people.
- Donnie's final hypnotherapy session. Dr. Thurman attempts to find the root of his problems, resulting in a regressed, childlike version of Donnie answering her questions. He's beginning to understand that "the end of the world" actually just means the end of his world, and is clearly terrified. He paces the room nervously while talking, grabs a stuffed animal almost unconsciously, and eventually breaks down after seeing Frank in the office, hiding his face in her neck and sobbing. It drives home how hard it is for him to deal with this; he's effectively a little kid caught alone in an apocalypse.
- This line from Frank.
I'm so sorry, Donnie.
- This makes sense, as he is one of the manipulated dead (long story), and is apologising in advance for killing Gretchen.